Thread-cutting device on sewing machines

ABSTRACT

A device for use in conjunction with sewing machines for cutting the thread between successive workpieces by means of a suction tube which is arranged on the delivery side of the stitch-forming point and which determines the position of the free thread and further by means of a pair of cutting blades of which one at least is driven.

United States Patent Inventor Helmut Schips Klrch str. 63:, 9400 Rorschach, Switzerland Appl. No. 23,239 Filed Mar. 27, 1970 Patented Nov. 30, 1971 Priority Apr. 2, 1969 Switzerland 5136/69 THREAD-CUTTING DEVICE 0N SEWING MACHINES 6 Claims, 4 Drawing Figs.

11.8. 112/252 Int. 1105b 65/06 FieldotSeareh 112/252 References Cited UNITED STATES PATENTS Butler Russell et al.

Daniel et al Hornberger, Sr.. Tiemann lizuka Strauss et a1 Primary ExaminerJames R. Boler AttorneyBrowdy & Niemark ABSTRACT: A device for use in conjunction with sewing machines for cutting the thread between successive workpieces by means of a suction tube which is arranged on the delivery side of the stitch-forming point and which determines the position of the free thread and further by means of a pair of cutting blades of which one at least is driven.

THREAD-CUTTING'DEVICE ON SEWING MACHINES The present invention concerns a device for use in conjunction with sewing machines for cutting the thread between successive workpieces by means of a suction tube which is arranged on the delivery side of the stitch-forming point and i which determines the position of the free thread and further by means of a pair of cutting blades of which one at least is driven.

Known systems for cutting the thread joining two successive workpieces have a suction tube which is arranged at a distance from the stitch-forming point of the sewing machine and which produces a suction air current parallel to the direction of the workpiece feed. In that arrangement, the free thread is first caught at a certain distance from the stitch-forming point by the suction air current and brought within reach of a pair of cutting blades which are arranged inside the suction tube and of which one is continually driven, and the thread is then cut. In order to prevent the workpiece from entering the suction tube during the workpiece feed, the opening of the suction tube is provided with a deflector plate having an opening and a slot corresponding to the thickness of the thread, so that the workpiece is deflected from the suction tube while the free thread is caught by the suction air current. While systems of that type cut with comparative dependability the free thread ahead of the leading workpiece end, they require special handling of the workpiece for cutting the thread at the trailing end of the workpiece. For this, as soon as the workpiece has left the stitch-forming point or the range of action of the feed tools, the operator must move it along a certain distance in the original feed direction, i.e. bring it to the suction tube, where it muststay for a short time and then, after cutting, be moved on again. If the movement of the workpiece to be performed by the operator is carried out at a speed which is equal to, or greater than, the stitch-forming speed, no thread slack can arise, and so the thread cannot be caught by the suction air current and therefore cannot be cut. Moreover, if the workpiece, having left the stitch-forming point, is not moved along in its original feed direction, but is instead pulled away obliquely, for instance, there will be no thread slack which can be caught by the suction air current, nor will the thread be brought within reach of the cutter. So, in this case again, the thread cannot be cut.

The object of the present invention is to provide a device for cutting the thread joining two successive workpieces which ensures the dependable cutting of the thread while obviating any need for additional movement of the workpiece after the actual feed movement and in the direction thereof.

For the purpose of achieving the said object, the invention provides the solution to the problem of designing and arranging the thread-cutting device in such a manner that the thread leaving the stitch-forming tongue can be caught by the suction air current and conveyed to the cutter when it leaves the range of action of the work feed tools.

The solution provided hereunder consists in that the suction tube produces a suction air current which is substantially perpendicular to the work feed direction, and that there is arranged between the suction air current and the stitch-forming tongue a guide piece which has a workpiece guide surface oblique to the work feed direction and which further has a forward end surface located within the range of the suction air current and spaced from the moving blade of the pair of cutting blades at a distance extending in the work feed direction. By this arrangement, as soon as the free thread leaves the range of action of the work feed means, i.e. as soon as it leaves the downstream row of teeth of the fabric feeder as viewed in the work feed direction, the suction air current pulls it away across the work feed direction and conveys it between the end surface of the guide piece and the end surface of the moving cutting blade into the suction tube. When the operator moves the workpiece out of the range of the stitch-forming point, a comparatively short movement of the workpiece, i.e. a movement measuring only a few millimeters is sufficient to bring the thread, which is already resting on the rigidly arranged lower cutting blade, to a point below the moving blade for cutting. As the workpiece, as soon as it has left the range of action of the work feed means, briefly stops in that position, there arises with certainty a thread slack which can be caught by the suction air current and which can then be cut by the pair of cutting blades practically independently of the movement of the workpiece away from the stitch-forming point.

A space-saving arrangement which also with certainty prevents any damage to the workpiece or, more particularly, to the seam formed thereon can be achieved by arranging the pair of cutting blades parallel to the work feed direction and covering both blades in the work feed direction by the forward end surface of the guide piece.

An arrangement that is simple in constructional respect is achieved by forming the guide piece integral with the support of the cutting blades.

An embodiment of the invention is now to be illustrated by way of example with reference to the accompanying drawing, in which FIG. I shows a side view of the thread-cutting device in which the workpiece moves from right to left during the work feed movement;

FIG. 2 shows a top view of the thread-cutting device;

FIG. 3 shows a side view of the pair of cutting blades, with the driving link and the driving bolt;

FIG. 4 shows a top view of FIG. 3, with a section of the driving lever.

In FIGS. 1 and 2, reference 1 indicates a cutting-blade sup port which is fixed to the sewing machine. A cutting blade 3 of the form shown in the drawings is fixed to the said support by bolts 5 and oriented parallel to the work feed direction. The blade support 1 is provided at its back or upstream end facing the stitch-fonning point with a guide piece 7 which presents a guide surface 8 oblique to the work feed direction and further presents a forward end surface 9. Fixed by a pivot bolt II to the blade support 1 or, more particularly, to the lower blade 3 connected to it, is an upper blade 10 which is provided at its end facing away from the knife edge with a bolting surface 14 for a driving link 16. The driving link is connected to the upper blade 10 by bolts 17 extending through oblong holes and presents a slot 18 to receive a driving bolt 19. The driving bolt 19 is provided with a screw thread and is screwed into a lever 27 (see FIG. 4) which is continually driven in a manner not shown and thus continually moves the upper blade I0 up and down. To ensure faultless cutting or shearing, a spring 22 is arranged between the lever 27 and the upper blade 10 to press the latter against the rigidly fixed lower blade 3.

As shown in particular in FIG. I, the arrangement of the upper blade 10 is such that between its end surface and the forward end surface 9 of the guide piece 7 there is a gap 26 through which a suction air current, produced by a suction tube 24, can draw the thread. The plane of the opening 25 of the suction tube 24 is parallel to the work feed direction and arranged behind the gap 26, so that the air current produced by the suction tube 24 is directed substantially across or transverse to the work feed direction and draws the free thread through the space between the end surface of the upper blade and the forward end surface 9 of the guide piece 7. Thus, the gap 26 ensures that the suction air current produced by the suction tube is not interrupted by the continual up-and-down movement of the upper blade 10.

During the formation of the free thread, the latter, as soon as it leaves the stitch-forming point, is caught within the range of the downstream toothing 30 of the fabric feeder 31 by the suction air current directed across the work feed direction. In the process, the thread rests on the lower blade 3 and is conveyed through the gap 26 to the suction tube 24. As the leading edge of the workpiece leaves the stitch-forming point, the thread is moved along in the feed direction by the feed movement of the workpiece, reaches a point under the upper blade 10 down continually moving up and down and is cut by the latter. As soon as the rear end of the workpiece leaves the rear downstream row of teeth 30 of the fabric feeder 31 and is therefore no longer moved along in the work feed direction by the fabric feeder, there is formed a thread slack which is caught by the suction air current and passed through the gap 26. When the workpiece is removed from the stitch-forming point, either by the operator or by the succeeding piece to be sewn, a slight movement, measuring only a few millimeters, of the workpiece is sufiicient to bring the thread, which is already resting on the lower blade 3, within reach of the upper blade-l for cutting.

The thread-cutting device described is extremely simple in construction, very compact and can therefore be easily attached to the machine. As it is also extremely slender (note FIG. 2) it can be arranged opposite the rear downstream row of teeth of the fabric feeder, in which case the guide surface 8 oblique to the work feed direction prevents the workpiece from entering the range of the cutting blades. By this arrangement it is also possible automatically to cut the thread at the end of the workpiece without involving any stopping thereof or any additional movement. As the thread is drawn away sideways, the cutting process is removed from the range of the workpiece and the normal work feed direction to give a clear view, so that, in the event of any trouble with cutting, it is easy to see the fault and intervene at once, without in any way affecting the work feed tools. Also, as the opening 25 of the suction tube 24 is displaced with respect to the upper blade 10 in the work feed direction and as there is a gap 26 between the end surface of the said upper blade and the forward end surface 9 of the guide piece 7, the opening of the suction tube 24 is at no moment closed by the pair of cutting blades 3,10.

This arrangement avoids any need of reforming the suction air current after every movement of the upper blade 10 and thus increases suction dependability. Both the upper and the lower blade are adjustable in cutting angle by bolts designed as adjusting screws. The spring 22, pressing the knife edge of the upper blade 10 against the lower blade 3, ensures a neat cut.

It is also possible to have the upper blade rigidly fixed and the lower blade moving. lnstead of installing cutting blades, it is possible to fit a cutter head or a filament for parting the thread by burning.

What is claimed is:

1. in a device for use in conjunction with sewing machines for cutting the thread between successive workpieces comprising a suction tube for placement at the delivery side of the stitch-forming point of a sewing machine, and a pair of cutting blades for cutting the thread caught by suction from the suction tube, the improvement comprising an elongated support adapted to be longitudinally oriented on a sewing machine along the direction of work feed;

means on said support to produce a lateral suction air current perpendicular to the longitudinal dimension of said support, said means including said suction tube;

a guide piece at the upstream end of said support for location between said means to produce suction air current and the stitch-forming tongue of the sewing machine, said guide piece having a workpiece guide surface at its upstream edge and oblique to the longitudinal dimension of said support, said guide piece further having a forward end located adjacent said means to produce suction;

and means on said support to carry said pair of cutting blades to provide intermeshing of said blades at a location along the longitudinal dimension of said support and immediately downstream from said forward end,

2. A device in accordance with claim 1 wherein said cutting blades are disposed parallel to the longitudinal dimension of said support, and wherein said forward end serves to cover said cutting blades.

3. A device in accordance with claim 1 wherein said guide piece is integral with said support.

4. A device in accordance with claim 1 further comprising spring means for maintaining said cutting blades tightly adjacent one another.

5. A device in accordance with claim 2 wherein a gap is provided between said forward end and said cutting blades.

. A device in accordance with claim 5 wherein said guide piece is triangular and is mounted with said oblique workpiece guide surface laterally adjacent the downstream row of teeth of the sewing machine fabric feeder, said suction tube being disposed vertically and placed laterally adjacent the third side of said triangular guide piece.

0 I i i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 621 731, Dated Nov. 30. 1971 Inventor(s) Helmut Schips It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 22 (Claim 1), insert --said lateral suction air current passing through the location of said intermeshing of said blades immediately downstream from said forward end."

Signed and sealed this 25th day of April 1972.

( SEAL) Attes t2 EDWARD MoFLETCHhJRJR. ROBERT GO'LTSCHALK Attesting Gffioer Commissioner of Patents ORM 530-1950 (10459) USCOMM-DC 60376-P69 a .5. GOVERNMENT PRlKING OFFICE I \99 0-555'33 

1. In a device for use in conjunction with sewing machines for cutting the thread between successive workpieces comprising a suction tube for placement at the delivery side of the stitchforming point of a sewing machinE, and a pair of cutting blades for cutting the thread caught by suction from the suction tube, the improvement comprising an elongated support adapted to be longitudinally oriented on a sewing machine along the direction of work feed; means on said support to produce a lateral suction air current perpendicular to the longitudinal dimension of said support, said means including said suction tube; a guide piece at the upstream end of said support for location between said means to produce suction air current and the stitch-forming tongue of the sewing machine, said guide piece having a workpiece guide surface at its upstream edge and oblique to the longitudinal dimension of said support, said guide piece further having a forward end located adjacent said means to produce suction; and means on said support to carry said pair of cutting blades to provide intermeshing of said blades at a location along the longitudinal dimension of said support and immediately downstream from said forward end,
 2. A device in accordance with claim 1 wherein said cutting blades are disposed parallel to the longitudinal dimension of said support, and wherein said forward end serves to cover said cutting blades.
 3. A device in accordance with claim 1 wherein said guide piece is integral with said support.
 4. A device in accordance with claim 1 further comprising spring means for maintaining said cutting blades tightly adjacent one another.
 5. A device in accordance with claim 2 wherein a gap is provided between said forward end and said cutting blades.
 6. A device in accordance with claim 5 wherein said guide piece is triangular and is mounted with said oblique workpiece guide surface laterally adjacent the downstream row of teeth of the sewing machine fabric feeder, said suction tube being disposed vertically and placed laterally adjacent the third side of said triangular guide piece. 